How to Calculate EPCRA Reporting Thresholds (With Examples)

The two federal threshold categories

EPCRA sets different baseline thresholds depending on what kind of chemical you're storing:

The EHS list and their specific TPQs are published by the EPA and don't follow a single flat number. Some EHS chemicals have TPQs well below 500 lbs, which is exactly why the rule says "whichever is lower."

• Hazardous chemicals (any chemical for which OSHA's Hazard Communication Standard requires you to maintain an SDS): 10,000 lbs
• Extremely Hazardous Substances (EHS), a specific EPA-designated list: 500 lbs, or the chemical's Threshold Planning Quantity (TPQ), whichever is lower

The rule that trips people up: maximum, not average

Thresholds are based on the maximum quantity present at your facility at any single point during the calendar year, not an average, and not what happens to be on-site on the day you do inventory. If you received a large shipment in June and drew it down to nearly nothing by December, June's peak quantity is what counts, not December's.

The reason is in how the rule is written: the comparison is against the maximum amount present at any one time during the reporting year, totalled across the whole facility rather than per container or per room. The threshold asks whether a given amount was ever on-site at once, which is the amount responders could face on that day. Tier II also asks for the average daily amount and the number of days on-site, but those are fields you complete after a chemical is reportable; they don't decide whether it is.

Worked example 1: A hazardous chemical

Say your facility (fictional) stores acetone, a hazardous chemical requiring an SDS, with no separate EHS listing. Over the year, your acetone inventory looked like this:

Even though your average holding was well under 10,000 lbs, the June peak of 12,500 lbs exceeded the threshold. This facility is required to report acetone on its Tier II filing for the year, using 12,500 lbs as the maximum quantity.

Worked example 2: An Extremely Hazardous Substance

Now say your facility stores a chemical listed as an EHS with a published TPQ of 300 lbs (a fictional value used for illustration only). Under the rule, you compare 500 lbs and the TPQ, and use whichever is lower: in this case, 300 lbs. If your maximum on-site quantity for that chemical during the year was 350 lbs, you've exceeded the 300 lb threshold and must report it, even though 350 lbs is well under the general 500 lb figure some people mistakenly use as a flat rule.

EHS and mixtures: the planning quantity versus the Tier II comparison

Example 2 used the same EHS data for two different checks, and it helps to keep them apart. The Threshold Planning Quantity (TPQ) is the Section 302 emergency-planning trigger: if an EHS is present at or above its TPQ, the facility notifies its SERC and LEPC. The Section 312 (Tier II) comparison uses a different number: 500 lbs or the TPQ, whichever is lower. When a chemical's TPQ is below 500 lbs, both checks use the TPQ. When its TPQ is above 500 lbs, the chemical becomes reportable on the Tier II at 500 lbs, before Section 302 is triggered at the TPQ.

Both checks start with confirming identity. Match the CAS number from the SDS against 40 CFR part 355, Appendices A and B, or EPA's consolidated List of Lists, which shows EHS status, TPQ and CAS number together. Our guide to the extremely hazardous substance list walks through that lookup and what to record.

Counting an EHS that sits inside mixtures

Under 40 CFR 370.14, the total for an EHS is the amount present as a component in all mixtures plus all other quantities of that EHS at the facility at any one time. A component's quantity is its concentration multiplied by the weight of the mixture, so you need the concentration (by weight) from SDS Section 3 and the mixture's weight. If a mixture is stored by volume, convert it to pounds using the density or specific gravity on the SDS before multiplying.

You may report either the component or the mixture as a whole, but for each mixture, use the same option in your Section 311 SDS reporting and your Section 312 inventory reporting where possible. For hazardous chemicals (not EHS), a component at 1% or less of a mixture need not be counted, or 0.1% or less if it is a carcinogen. That cut-off is written for hazardous chemicals, so don't apply it to an EHS component without checking 40 CFR 370.14.

Why state-specific thresholds matter just as much as federal ones

The federal thresholds above are a floor, not a ceiling. A number of states set their own, more restrictive thresholds for some chemicals, add reporting obligations for substances not federally listed as EHS, or apply lower thresholds to specific categories like fuels stored at retail facilities. A facility can be entirely correct under the federal calculation and still be out of compliance with its state's rule if it stops there.

This is one of the most overlooked parts of threshold calculation, because most general EPCRA guidance, including the federal thresholds above, describes only the national baseline. Your actual reporting obligation is the more restrictive of the federal threshold and whatever your specific state requires.

What tends to vary state by state

Because these variations are set independently by each state's SERC or environmental agency, there's no substitute for checking your specific state's requirements directly rather than assuming the federal numbers are the whole picture.

• Lower thresholds for specific chemicals or chemical categories than the federal 10,000 lb / 500 lb baseline
• Additional state-designated hazardous substances not on the federal EHS list
• Different treatment of mixtures: some states require reporting a mixture's components individually, even below federal thresholds for the mixture as a whole
• State-specific exemptions or thresholds for retail fuel storage, agricultural chemicals, or other specific facility types
• Different rounding or aggregation rules when the same chemical is stored in multiple containers or locations on-site

A practical way to handle this

Calculate against the federal threshold first, since it applies everywhere as the baseline. Then check your state's specific requirements for the same chemical. If the state threshold is lower, or the chemical is separately state-listed, that's the number that actually governs your reporting obligation for that facility. Doing this at the facility level matters too: a company operating in multiple states can have the same chemical be reportable in one state and not another, at the exact same on-site quantity.

Common threshold calculation mistakes

• Using average inventory instead of the maximum quantity present at any point in the year
• Applying the flat 500 lb EHS threshold without checking whether the specific chemical's TPQ is actually lower
• Assuming the federal threshold is the only one that applies, without checking state-specific rules
• Forgetting to aggregate the same chemical stored in multiple locations or containers across the facility
• Overlooking chemicals in mixtures: a chemical can trigger reporting as a component of a blended product, not just in its pure form
• Not re-checking thresholds mid-year when a new shipment or new process introduces a chemical that wasn't previously tracked

Special threshold cases worth knowing

A few categories have their own distinct rules rather than the standard 10,000 lb / 500 lb framework:

• Retail gasoline stations: a 75,000-gallon federal threshold applies to gasoline stored entirely in underground storage tanks that comply with applicable underground storage tank requirements, though some states apply different conditions
• Retail diesel: a 100,000-gallon federal threshold applies under the same underground-storage conditions
• Certain substances used in research, or packaged for consumer retail sale, may fall under specific EPCRA exemptions, but these exemptions have conditions and shouldn't be assumed without checking the specific rule, federal or state

Why threshold errors are usually invisible until it's too late

Because thresholds depend on a single peak moment during the year, and potentially on a state-specific number lower than the federal one, a facility can easily believe it's under the limit based on typical operating inventory and the federal figure alone. A seasonal spike or an unreviewed state rule could have quietly pushed it over. Continuous tracking against both federal and state-specific thresholds, rather than a single point-in-time count near the filing deadline, is the only reliable way to catch this.

Official source

The federal requirements described in this article are established under the Emergency Planning and Community Right-to-Know Act (EPCRA). Always verify current state-specific rules with your SERC.

Threshold and mixture rules for Sections 311 and 312 are in 40 CFR part 370; Section 302 and the EHS list with TPQs are in 40 CFR part 355. EPA's EPCRA Sections 311-312 page summarizes the thresholds and deadlines.